Electrochemical gas sensors are typically used to determine the composition of a gas and may further be used to detect the presence of various elements or compounds in a gas.
For example, electrochemical sensors may be used in medical care equipment, such as an oxygen inhalation machine, to detect the amount of oxygen remaining in the reservoir or given to the patient. Electrochemical sensors may also be used in environmental situations for detecting the presence of dangerous chemical compounds in an unknown gas.
U.S. Pat. No. 5,431,806 (“806 patent”), U.S. Pat. No. 5,492,611 (“611 patent”), and U.S. Pat. No. 5,478,460 (“460 patent”) disclose an electrochemical gas sensor having a permeable membrane. These types of sensors typically measure gas by diffusing it through the membrane and dissolving it in an electrolyte on the other side of the membrane. The electrolyte is in contact with electrodes, which in turn typically measure current flow as a function of oxygen concentrations.
A disadvantage with a gas diffusion sensor is that the sensor's sensitivity is compromised. This is due to the indirect contact between the gas and the electrode or electrolyte. Gas that dissolves in the electrolyte may be carried downstream with the flow of electrolyte and may disadvantageously affect current readings and reduce sensor sensitivity. Further, the time for gas to permeate through the membrane and dissolve in the electrolyte may further negatively affect a sensor's response time.
U.S. Pat. No. 5,670,031 (“031 patent”) is directed to an electrochemical sensor having a plurality of micro electrodes in series and in close proximity to one another. This sensor typically operates by measuring differences in current flow between one pair of electrodes to the next along a length of a channel in which electrolyte flows. Because minute changes in current flow can be measured, accuracy is generally believed to be improved.
Nowhere is it claimed or disclosed in the prior art that a sensor's sensitivity can be improved by measuring the gas as it directly comes in contact with both electrolyte and electrode. The '806, '611, and '460 patents all claim a gas permeable membrane through which the gas permeates in order to be measured. The '031 patent is directed to improving the sensitivity by optimizing the contact points between the electrode and electrolyte.
Furthermore, nowhere is it claimed or disclosed in the prior art that a sensor provides a channel for transporting, holding, or receiving gas for enabling direct contact with the electrode and electrolyte for measurement.
What is desired, therefore, is to provide an electrochemical gas sensor having improved sensitivity. What is also desired is to provide an electrochemical gas sensor having an improved response time between the time gas is introduced into the sensor and when a measurement is made.